State-of-art scalable hierarchical coding methods allow encoding the information hierarchically in order that it can be decoded at different resolution and/or quality levels. A data stream generated by a scalable coding device is thus divided into several layers, a base layer and one or more enhancement layers. These devices allow adapting a unique data stream to variable transmission conditions (bandwidth, error rate . . . ) and also to the capacities of reception devices (CPU, characteristics of reproduction device . . . ). A spatially scalable hierarchical encoding (or decoding) method encodes (or decodes) a first part of data called base layer relating to low resolution pictures also called base layer pictures (BL pictures), and from this base layer encodes (or decodes) at least another data part called enhancement layer relating to high resolution pictures also called high layer pictures (HL pictures) or enhancement layer pictures. The motion data relating to the enhancement layer is possibly inherited (i.e. derived) from motion data relating to the base layer by a method called inter-layer prediction method or inter-layer inheriting method. Therefore each macroblock of a high resolution picture is predicted either according to a classical spatial or temporal prediction mode (e.g. intra prediction, bidirectional prediction mode, direct prediction mode, forward/backward prediction . . . ) or according to an inter-layer prediction mode. In this former case, motion data associated to a high resolution macroblock has to be derived or inherited from motion data (also called motion information) associated to macroblocks of low resolution pictures whatever the format of the low or high resolution pictures is, i.e. progressive or interlace. In this context the expression “motion data” includes not only motion vectors but more generally coding information such as partitioning pattern associated to macroblock/block of pixels of the high resolution picture for splitting said macroblock/block into several sub-blocks, coding modes associated to said blocks and picture reference indices associated to some blocks allowing to reference the picture used to predict said block.